\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{circuitikz}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes}
\ctikzset{bipoles/length=1cm}
\begin{document}
\small
\begin{circuitikz}[>=latex, scale=1,european]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
\draw (0,1.0)--(0,0)--(.9,0);
\draw (.9,2.4) to [american inductor] (.9,0);
\draw (.9,2.4)--(0,2.4)--(0,1.4) ;
\draw (1.5,0)--(5,0) to [R=$R$,name=dz] (5,2.4) --(1.5,2.4) node[above]{$a$};
\draw (1.50,0)node[below]{$b$} to  [american inductor,name=xq] (1.5,2.4);
\ctikzset{diodes/scale=0.6}\draw (1.5,2.4) to[full diode=$D$](5,2.4);
 \draw (0,1.0) [fill=white]circle (1.5pt);
        \draw (0,1.4) [fill=white]circle (1.5pt);
        \node at (0,1.2){$\sim$};
\draw [ultra thick](1.2,0.8)--(1.2,1.6);   
\node at (1.2,2.0){$B$};
\draw [<->](2.25,0)--(2.25,2.4)node [midway,right]{$u$} ;
\draw [<->](3.7,0)--(3.7,2.4)node [midway,right]{$u_R$};
\node at (dz.left)[right=1mm]{$-$}; 
\node at (dz.right)[right=1mm]{$+$};
\end{circuitikz}
\end{document}